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Re-invent ReadMoreState
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@fornewid
fornewid committed Dec 21, 2024
1 parent 4675898 commit 6480521
Showing 1 changed file with 95 additions and 98 deletions.
193 changes: 95 additions & 98 deletions ...oundation/src/main/java/com/webtoonscorp/android/readmore/foundation/BasicReadMoreText.kt
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Original file line number Diff line number Diff line change
Expand Up @@ -29,11 +29,11 @@ import androidx.compose.runtime.mutableStateOf
import androidx.compose.runtime.remember
import androidx.compose.runtime.setValue
import androidx.compose.ui.Modifier
import androidx.compose.ui.geometry.Rect
import androidx.compose.ui.text.AnnotatedString
import androidx.compose.ui.text.LinkAnnotation
import androidx.compose.ui.text.SpanStyle
import androidx.compose.ui.text.TextLayoutResult
import androidx.compose.ui.text.TextMeasurer
import androidx.compose.ui.text.TextStyle
import androidx.compose.ui.text.buildAnnotatedString
import androidx.compose.ui.text.rememberTextMeasurer
Expand All @@ -42,7 +42,6 @@ import androidx.compose.ui.text.withLink
import androidx.compose.ui.text.withStyle
import androidx.compose.ui.unit.Constraints
import androidx.compose.ui.unit.dp
import kotlin.math.max

/**
* Basic element that displays text with read more.
Expand Down Expand Up @@ -243,13 +242,7 @@ private fun CoreReadMoreText(
}

val textMeasurer = rememberTextMeasurer()

val state = remember(text, readMoreMaxLines) {
ReadMoreState(
originalText = text,
readMoreMaxLines = readMoreMaxLines,
)
}
val state = remember { ReadMoreState() }

val currentText = buildAnnotatedString {
if (expanded) {
Expand Down Expand Up @@ -317,34 +310,16 @@ private fun CoreReadMoreText(
readMoreMaxLines,
softWrap,
) {
Log.d(Tag, "LaunchedEffect: $text")
val overflowTextWidth = if (overflowText.isNotEmpty()) {
textMeasurer.measure(
text = overflowText,
style = style,
).size.width
} else {
0
}
val readMoreTextWidth = if (readMoreTextWithStyle.isNotEmpty()) {
textMeasurer.measure(
text = readMoreTextWithStyle,
style = style.merge(readMoreStyle),
).size.width
} else {
0
}
val textLayout = textMeasurer.measure(
text = text,
state.applyCollapsedText(
textMeasurer = textMeasurer,
constraints = constraints,
overflowText = overflowText,
readMoreTextWithStyle = readMoreTextWithStyle,
style = style,
maxLines = readMoreMaxLines,
overflow = TextOverflow.Ellipsis,
readMoreStyle = readMoreStyle,
text = text,
readMoreMaxLines = readMoreMaxLines,
softWrap = softWrap,
constraints = constraints,
)
state.onTextLayout(
result = textLayout,
decorationWidth = overflowTextWidth + readMoreTextWidth,
)
}
}
Expand All @@ -358,13 +333,7 @@ private const val DebugLog = false
private const val Tag = "ReadMoreState"

@Stable
private class ReadMoreState(
private val originalText: AnnotatedString,
private val readMoreMaxLines: Int,
) {
private var lastTextLayout: TextLayoutResult? = null
private var lastDecorationWidth: Int? = null

private class ReadMoreState {
private var _collapsedText: AnnotatedString by mutableStateOf(AnnotatedString(""))

var collapsedText: AnnotatedString
Expand All @@ -381,74 +350,102 @@ private class ReadMoreState(
val isCollapsible: Boolean
get() = collapsedText.isNotEmpty()

fun onTextLayout(result: TextLayoutResult, decorationWidth: Int) {
val decorationChanged = this.lastDecorationWidth != decorationWidth
if (decorationChanged) {
if (DebugLog) {
Log.d(Tag, "onTextLayout: decorationTextWidth ${this.lastDecorationWidth} -> $decorationWidth")
}
this.lastDecorationWidth = decorationWidth
fun applyCollapsedText(
textMeasurer: TextMeasurer,
constraints: Constraints,
overflowText: String,
readMoreTextWithStyle: AnnotatedString,
style: TextStyle,
readMoreStyle: SpanStyle,
text: AnnotatedString,
readMoreMaxLines: Int,
softWrap: Boolean,
) {
val overflowTextWidth = if (overflowText.isNotEmpty()) {
textMeasurer.measure(
text = overflowText,
style = style,
).size.width
} else {
0
}

val lastLineIndex = readMoreMaxLines - 1
val previous = lastTextLayout
val old = previous != null &&
previous.lineCount >= readMoreMaxLines &&
previous.isLineEllipsized(lastLineIndex)
val new = result.lineCount >= readMoreMaxLines &&
result.isLineEllipsized(lastLineIndex)
val textChanged = previous != result && old != new
if (textChanged) {
if (DebugLog) {
Log.d(Tag, "onTextLayout:")
}
lastTextLayout = result
val readMoreTextWidth = if (readMoreTextWithStyle.isNotEmpty()) {
textMeasurer.measure(
text = readMoreTextWithStyle,
style = style.merge(readMoreStyle),
).size.width
} else {
0
}
val textLayout = textMeasurer.measure(
text = text,
style = style,
maxLines = readMoreMaxLines,
overflow = TextOverflow.Clip,
softWrap = softWrap,
constraints = constraints,
)

if (decorationChanged || textChanged) {
updateCollapsedText(
textLayout = result,
decorationWidth = decorationWidth,
)
val clipTextCount = textLayout.getLineEnd(lineIndex = textLayout.lineCount - 1)
val isLineClipped = text.count() > clipTextCount
if (isLineClipped) {
val countUntilMaxLine =
textLayout.getLineEnd(readMoreMaxLines - 1, visibleEnd = true)

val decorationWidth = overflowTextWidth + readMoreTextWidth
val replaceCount = text
.substringOf(textLayout, line = readMoreMaxLines)
.calculateReplaceCountToBeSingleLineWith(
maximumTextWidth = constraints.maxWidth - decorationWidth,
measureTextWidth = { subText ->
textMeasurer.measure(
text = subText,
style = style,
softWrap = softWrap,
).size.width
},
)
collapsedText = text.subSequence(0, countUntilMaxLine - replaceCount)
} else {
collapsedText = AnnotatedString("")
}
if (DebugLog) {
Log.d(Tag, "applyCollapsedText: collapsedText=$collapsedText")
}
}

private fun updateCollapsedText(
textLayout: TextLayoutResult,
decorationWidth: Int,
) {
val lastLineIndex = readMoreMaxLines - 1
if (textLayout.lineCount >= readMoreMaxLines &&
textLayout.isLineEllipsized(lastLineIndex)
) {
val countUntilMaxLine = textLayout.getLineEnd(readMoreMaxLines - 1, visibleEnd = true)
val countUntilMaxLineExceptNewline: Int =
if (originalText.getOrNull(countUntilMaxLine) == '\n') {
// Workaround:
// If the last character of the sentence is a newline char('\n'),
// calculates excluding the last newline char('\n').
countUntilMaxLine - 1
} else {
countUntilMaxLine
}
val maximumWidth = max(0, textLayout.layoutInput.constraints.maxWidth - decorationWidth)
var replacedEndIndex = countUntilMaxLineExceptNewline + 1
var currentTextBounds: Rect
do {
replacedEndIndex -= 1
currentTextBounds = textLayout.getCursorRect(replacedEndIndex)
} while (currentTextBounds.left > maximumWidth)
collapsedText = originalText.subSequence(startIndex = 0, endIndex = replacedEndIndex)
if (DebugLog) {
Log.d(Tag, "updateCollapsedText: collapsedText=$collapsedText")
private fun AnnotatedString.substringOf(layout: TextLayoutResult, line: Int): AnnotatedString {
val lastLineStartIndex = layout.getLineStart(line - 1)
val lastLineEndIndex = layout.getLineEnd(line - 1, visibleEnd = true)
return subSequence(lastLineStartIndex, lastLineEndIndex)
}

private inline fun AnnotatedString.calculateReplaceCountToBeSingleLineWith(
maximumTextWidth: Int,
measureTextWidth: (subText: AnnotatedString) -> Int,
): Int {
var replacedTextWidth: Int
var replacedCount = -1
do {
replacedCount++
replacedTextWidth = measureTextWidth(
subSequence(0, this.length - replacedCount)
)
} while (replacedCount < this.length && replacedTextWidth >= maximumTextWidth)

val lastVisibleChar: Char? = this.getOrNull(this.length - replacedCount - 1)
val firstOverflowChar: Char? = this.getOrNull(this.length - replacedCount)
if (lastVisibleChar?.isSurrogate() == true && firstOverflowChar?.isHighSurrogate() == false) {
val subText = subSequence(0, this.length - replacedCount)
if (subText.isNotEmpty()) {
return length - subText.indexOfLast { it.isHighSurrogate() }
}
}
return replacedCount
}

override fun toString(): String {
return "ReadMoreState(" +
"originalText=$originalText, " +
"readMoreMaxLines=$readMoreMaxLines, " +
"collapsedText=$collapsedText" +
")"
}
Expand Down

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